The present invention relates to a semiconductor integrated circuit and an operating method thereof, and particularly to a technique effective in reducing the time of reception operation switching between multiple wireless systems.
A radio frequency (RF) signal processing circuit configured as a receiver incorporated in a cellular phone terminal etc. converts a high-frequency signal received from an antenna into a baseband signal in a lower frequency band with high quality (e.g., low noise, suppression of signals in an interference band outside a desired signal band). On the other hand, with improvements in semiconductor device process technology and semiconductor circuit technology in recent years, in the field of the cellular phone terminal etc., a radio frequency signal processing circuit that supports multiple wireless access systems is integrated in a single semiconductor chip. The wireless access systems include, for example, GSM, EDGE, W-CDMA, HSDPA, and LTE systems. GSM is an abbreviation for “Global System for Mobile Communications”, EDGE is an abbreviation for “Enhanced Data for GSM Evolution: Enhanced Data for GPRS”, and GPRS is an abbreviation for “General Packet Radio Service”. W-CDMA is an abbreviation for “Wideband Code Division Multiple Access”, HSDPA is an abbreviation for “High Speed Downlink Packet Access”, and LTE is an abbreviation for “Long Term Evolution”.
The semiconductor chip incorporating the above-described radio frequency signal processing circuit converts reception analog baseband signals into reception digital baseband signals, which are transferred to a baseband LSI (Large Scale Integrated Circuit) through a digital interface.
The following Non-patent Document 1 describes a single-chip dual-mode 8-band CMOS transceiver which can support W-CDMA(HSDPA) and GSM(EDGE) systems, four bands of 800 MHz, 1.5 GHz, 1.7 GHz, 2 GHz in W-CDMA, and four bands of 850 MHz, 900 MHz, 1.8 GHz, 1.9 GHz in GSM/EDGE. The transceiver includes A/D and D/A converters, digital filters, and a 312 MHz low voltage differential signaling (LVDS) interface. For a transmitter chain, linear direct quadrature modulation architecture is commonly used for both the W-CDMA (HSDPA) and GSM(EDGE) systems. For a direct conversion receiver chain, analog baseband blocks (ABB), i.e., low-pass filters (LPF) and variable gain amplifiers (VGA), delta-sigma A/D converters, and FIR filters are used for both the W-CDMA(HSDPA) and GSM(EDGE) systems to reduce chip area. The characteristics of the analog baseband blocks (ABB) are reconfigurable by register-based control sequence. The receiver chain includes high-speed DC offset cancellers both in analog and digital stages, and an autonomous AGC controller with parameters such as time constants freely programmable by digital baseband (DBE) control.
A radio frequency (RF) signal processing circuit configured as a transmitter incorporated in the cellular phone terminal etc. is also integrated in the single semiconductor chip. Accordingly, transmission digital baseband signals generated from the baseband LSI are transferred through the digital interface to the radio frequency (RF) signal processing circuit configured as the transmitter integrated in the single semiconductor chip. The transmission digital baseband signals are converted into transmission analog baseband signals by D/A converters. Thus, reception digital baseband signals and transmission digital baseband signals are transferred through the digital interface between the radio frequency (RF) signal processing circuit configured as the receiver and transmitter, i.e., a transceiver integrated in the single semiconductor chip and the baseband LSI. Further, digital control signals for controlling the internal operation of the radio frequency (RF) signal processing circuit are supplied from the baseband LSI through the digital interface to the radio frequency (RF) signal processing circuit.
On the other hand, the baseband LSI deinterleaves interleaved signals and performs predetermined digital signal processing such as error correction.
The following Patent Document 1 describes a handover for continuing communication by switching cells when user equipment (UE) moves from one cell to another in a mobile communication system comprised of a plurality of cells. When the user equipment (UE) moves to an adjacent cell and a signal from the adjacent cell has become stronger than a signal from an originally-communicating serving cell, a handover to the adjacent cell is performed. Accordingly, the signal power of the adjacent cell is measured prior to the handover. The measurement result that the signal from the adjacent cell has become stronger than the signal from the serving cell is reported from the user equipment (UE) to a base station. Upon receiving this event, the base station determines execution of the handover and executes a handover procedure. Further, Patent Document 1 also describes a handover in the LTE system which is a successor to the W-CDMA and HSDPA systems.
As described above, in the mobile communication system, when the communication situation of one wireless access system in current communication becomes deteriorated, the radio field intensity of another wireless access system is measured to switch to the another wireless access system without delay. To perform this measurement, for such a short time of the order of several milliseconds that is imperceptible to the user, transmission and reception by the wireless access system in current communication are interrupted, and the semiconductor chip incorporating the radio frequency (RF) signal processing circuit is switched to the reception mode of the another wireless access system. In this measurement, it is not necessary to set the transmission mode of the semiconductor chip incorporating the radio frequency (RF) signal processing circuit to the another wireless access system.
The following Patent Document 2 describes the state confirmation of IEEE802.11e which is one system of the wireless LAN during wireless communication by IEEE802.11n which is another system of the wireless LAN.
[Patent Document 1]
    International Publication WO2009/057520A1 Specification[Patent Document 2]    Japanese Unexamined Patent Publication No. 2008-113149[Patent Document 3]    Japanese Unexamined Patent Publication No. 2010-245673[Non-Patent Document 1]    H. Yoshida et al, “A Single-Chip 8-Band CMOS Transceiver for W-CDMA(HSPA)/GSM(GPRS)/EDGE with Digital Interface”, ESSCIRC (European Solid-State Circuits Conference) 2008, PP. 142-145.[Non-Patent Document 2]    Daniel Kaczman et al, “A Single-Chip Tri-Band (2100, 1900, 850/800 MHz) WCDMA/HSDPA Cellular Transceiver”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 41, NO, 5, PP. 1122-1132, May 2005.[Non-Patent Document 3]    Tirdad Sowlati et al, “Quad-Band GSM/GPRS/EDGE Polar Loop Transmitter”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 39, NO. 12, PP. 2179-2189, December 2004.[Non-Patent Document 4]    Toshihiko Shimizu et al, “A Small GSM Power Amplifier Module Using Si-LDMOS Driver MMIC”, 2004 IEEE International Solid-State Circuits Conference Digest of Technical Papers, PP. 196-197, Feb. 17, 2004.